Self-adhesive compound and use thereof in an adhesive tape

ABSTRACT

A self-adhesive compound comprising a) at least one elastomer, at least one type of polybutadiene block copolymer being used as an elastomer, b) at least one partially hydrogenated hydrocarbon resin having a softening temperature of at least 90° C., c) at least one additional hydrocarbon resin, a terpene phenol resin and/or a colophonium resin having a softening temperature of at least 90° C., d) a soft resin, and e) additional additives as applicable.

This is a 371 of PCT/EP2014/056664 filed 3 Apr. 2014, which claimsforeign priority benefit under 35 U.S.C. 119 of German PatentApplication 10 2013 206 624.4 filed Apr. 15, 2013, the entire contentsof which are incorporated herein by reference.

The invention relates to a pressure-sensitive adhesive and also to theuse thereof in a pressure-sensitive adhesive strip comprising at leastone layer, which is redetachable without residue or destruction byextensive stretching substantially in the bond plane.

BACKGROUND OF THE INVENTION

Pressure-sensitive adhesives (PSAs) are adhesives which permit a durablejoin to the substrate even under relatively weak applied pressure andwhich after use can be detached from the substrate again substantiallywithout residue. At room temperature, PSAs have a permanentlypressure-sensitively adhesive effect, hence having a sufficiently lowviscosity and a high initial tack, so that they wet the surface of theparticular bonding base even under low applied pressure. The bondabilityof the adhesives derives from their adhesive properties, and theredetachability from their cohesive properties.

Included in particular under this heading are compounds which possesspressure-sensitively adhesive properties in accordance with the“Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas(Satas & Associates, Warwick 1999), especially those which meet theDahlquist criterion.

Elastically or plastically highly extensible pressure-sensitive adhesivestrips which can be detached again without residue or destruction byextensive stretching in the bond plane are known from, for example, U.S.Pat. No. 4,024,312 A, DE 33 31 016 C2, WO 92/01132 A1, WO 92/11333 A1,DE 42 22 849 A1, WO 95/06691 A1, DE 195 31 696 A1, DE 196 26 870 A1, DE196 49 727 A1, DE 196 49 728 A1, DE 196 49 729 A1, DE 197 08 364 A1, DE197 20 145 A1, DE 198 20 854 A1 and DE 100 03 318 A1, and are alsoreferred to below as strippable pressure-sensitive adhesive strips.

Strippable self-adhesive tapes of this kind are used frequently in theform of single- or double-sidedly pressure-sensitively adhesiveadhesive-sheet strips, which preferably have a nonpressure-sensitivelyadhesive grip region, from which the detachment operation is initiated.

Fields of use of aforesaid strippable pressure-sensitive adhesive stripsinclude in particular the residueless and nondestructively redetachablefixing of light to moderately heavy articles in the home, workplace, andoffice. In these applications they replace conventional fastening meanssuch as, for example, drawing pins, roundhead needles, thumb tacks,nails, screws, conventional self-adhesive tapes, and liquid adhesives.Key to the successful use of the pressure-sensitive adhesive strips isnot only the possibility of residueless and nondestructive redetachmentof bonded articles, but also their quick and easy bonding and also theirsecure hold for the envisaged period of bonding. It should be borne inmind in particular here that the adhesive strips must function on alarge number of substrates, in order to be able to serve as a universalfixing in the home, workplace, and office.

Pressure-sensitive adhesive strips of these kinds are availablecommercially, in the form of the tesa Powerstrips® and 3M CommandAdhesives.

Very high holding performance has been realizable to date, commercially,only with styrene block copolymer-based PSAs. These styrene blockcopolymers always include unsaturated polydiene blocks. Polydienes areintrinsically susceptible to thermooxidative aging and may be damaged byradiation and ozone.

A further key aspect of such strips, especially when they are to be usedon transparent surfaces such as windows, is their transparency.

tesa markets strippable transparent products with moderate holdingperformance as tesa Powerstrips® Deco. 3M offers transparent adhesivestrips featuring a holding performance of up to 900 g.

Approaches to creating transparent strippable adhesive products includethe utilization of styrene block copolymers which comprise hydrogenatedpolydiene blocks (DE 10 2007 021 504 A1 and U.S. Pat. No. 7,309,524 B).Although high transparency and improved aging stability are possiblewith the solution outlined, the requisitely high bonding performances,and especially the tear resistance, are not achievable via theseformulation approaches.

EP 1 418 212 A1 describes transparent adhesive strips, redetachablewithout residue or destruction, which are of triple-ply design. In thisarrangement, the middle layer contributes the major part of themechanical properties to the product properties, but is unstable towardUV light and ozone on account of its formulation. The outer layers takeon a filter function for ozone and UV light. A disadvantage of thisapproach is its multilayerness, which necessitates a multistageproduction process. Furthermore, the achievable holding performances arelimited due to the adhesive formulation forming the outer layers.

Also known are polyacrylate-based systems (WO 2010/077541 A1; WO2010/078346 A1; WO 2010/077435 A1; U.S. Pat. No. 6,723,407 B1), andthere are also descriptions of polysiloxane-based adhesive strips,including in U.S. Pat. No. 6,569,521 B1 and WO 2009/114683 A1.Advantages are their optical properties and the resistance. Thetension/extension properties and the balance between holding performanceand bonding performance, however, are not at a level allowinghigh-performance adhesive strips to be produced. In some such cases,sufficient tear strengths are achievable only through use of a carrier.

Multilayer products or those which include carriers always have thedisadvantage either that highly specific machines are required forproduction, or that a multiplicity of individual process steps have tobe carried out. Both of these are detrimental to the production costs.

The object is therefore to provide pressure-sensitive adhesives whichexhibit high holding and bonding performance, high transparency, minimaltinting, and sufficient stability with respect to light, heat, andozone, and sufficient tear strength, and also self-adhesive productscomprising such pressure-sensitive adhesives. Correspondingself-adhesive products are preferably of single-layer (carrier-free)design.

This object is achieved by means of a pressure-sensitive adhesive asrecorded in the main claims. The dependent claims provide advantageousdevelopments of the pressure-sensitive adhesive, and uses of thepressure-sensitive adhesive in pressure-sensitive adhesive strips.

SUMMARY OF THE INVENTION

The invention relates accordingly to a pressure-sensitive adhesive atleast comprising

-   (a) at least one elastomer, the elastomer having a fraction of at    least 40 wt %, based on the adhesive composition, and elastomer used    comprising at least one kind of a polybutadiene block copolymer,-   (b) at least one partly hydrogenated hydrocarbon resin (resin    kind 1) having a softening temperature of at least 90° C.,-   (c) optionally at least one further hydrocarbon resin, a    terpene-phenolic resin and/or a rosin having a softening temperature    of at least 90° C. (resin kind 2),-   (d) optionally a plasticizing resin,-   (e) optionally further additives.

The invention further relates to a pressure-sensitive adhesive at leastcomprising

-   (a) at least one elastomer, the elastomer having a fraction of at    least 40 wt %, based on the adhesive composition, and elastomer used    comprising at least one kind of a polybutadiene block copolymer,-   (b) at least one nonhydrogenated hydrocarbon resin (resin kind 1)    having a softening temperature of at least 90° C.,-   (c) at least one further at least partly hydrogenated or    disproportionated hydrocarbon resin, terpene-phenolic resin and/or    rosin having a softening temperature of at least 90° C. (resin kind    2),-   (d) optionally a plasticizing resin,-   (e) optionally further additives.

DETAILED DESCRIPTION

The pressure-sensitive adhesive (PSA) is advantageously formulated suchthat it has a specific viscoelastic behavior. Viscoelastic behavior isdisplayed by many polymers and all PSAs. Their mechanical properties aredistinguished by a combination of elastic and viscous components(regarding the viscoelasticity, see, for example, J. D. Ferry,Viscoelastic Properties of Polymers, 3^(rd) edn., 1980, J. Wiley,Hoboken, pages 1 to 3). The reason for this is the required ozoneresistance, which in the case of extensible materials is dependent notonly on the chemical properties of the formula ingredients (K. W. Ho, J.Polym. Sci. A—Polym. Chem., 1986, 24, pages 2467 to 2482) and the effectof any ozone protectants (H. Fries, Gummi Fasern Kunststoffe, 1987, 40,pages 238 to 257; R. F. Ohm, Rubber World, 1993, 208, pages 18 to 22)but also on the mechanical properties (M. Braden, A. N. Gent, J. Appl.Polym. Sci., 1960, 3, pages 90 to 99).

The ozone resistance is particularly relevant for the detachment of theadhesive strips. Where detachment takes place with extension, therebypermitting substrate destruction and residues of adhesive to be avoided,a high tear strength on the part of the adhesive strips is adesideratum. The tear strength can be adjusted effectively through blockcopolymers, but ozone damage may exert a significantly adverse effect onthe susceptibility to tearing.

The usual ways of improving ozone resistance in rubber formulations arenot suitable for transparent adhesive strips. For instance, additivationwith waxes, which form a thin surface film over the rubber formulationthat acts as a barrier toward ozone, causes a reduction in theself-adhesive properties of the adhesive strip. Chemical antiozonantsare always colored, and, added even in small amounts, lead toperceptible tinting of the transparent adhesive strips.Polybutadiene-based block copolymers are distinguished overall by betteraging stability than polyisoprene-based systems, and so formulations ofthe invention comprise polybutadiene-based block copolymers as anelastomer component.

According to the teaching of Gent (M. Braden, A. N. Gent, J. Appl.Polym. Sci., 1960, 3, pages 90 to 99), the viscoelastic properties alsohave an influence on ozone resistance. For systems comprisingpolybutadiene block copolymer, this can be illustrated by looking at theozone resistance of pure (unformulated) polybutadiene block copolymersand comparing the results with adhesives which comprise polybutadieneblock copolymers that are the same but are already formulated withtackifying resins. On account of their double bonds present in thepolybutadiene blocks, the pure polybutadiene block copolymers arechemically reactive toward ozone (K. W. Ho, J. Polym. Sci. A—Polym.Chem., 1986, 24, pages 2467 to 2468). An assumed possible mechanism isthat known as the Criegee mechanism, via which attack on the main-chaindouble bond may be accompanied by chain scission within thepolybutadiene block.

For the more precise description and quantification of the extent ofelastic and viscous components, and also of the ratio of the componentsto one another, it is possible to employ the variables of storagemodulus (G′), loss modulus (G″), and the ratio G″/G′, identified as lossfactor tan δ (tan delta), which can be determined by Dynamic MechanicalAnalysis (DMA) (see test J). G′ is a measure of the elastic component,G″ a measure of the viscous component of a substance. Both variables aredependent on the deformation frequency and the temperature.

The loss factor tan δ is a measure of the elasticity and the flowcapacity of the substance under investigation.

The variables can be determined using a rheometer. In this case, thematerial under investigation is exposed to a sinusoidally oscillatingshearing stress in, for example, a plate/plate arrangement. In the caseof instruments operating with shear stress control, the deformation ismeasured as a function of time, and the time offset of this deformationγ (gamma) relative to the introduction of the shearing stress τ (tau) ismeasured. This time offset (phase shift between shear stress vector anddeformation vector) is identified as phase angle δ (delta). Thederivations are as follows:

Storage modulus G′ G′=τ/γ·cos(δ)

Loss modulus G″ G″=τ/γ·sin(δ)

Loss factor tan δ tan δ=G′/G″

The reports of the aforementioned parameters within this specificationpertain to measurement by means of a rheometer in plate-on-plateconfiguration, based on a circular sample having a diameter of 25 mm anda thickness of 1 mm. The temperature is 25° C.; otherwise, standardconditions prevail.

In accordance with the invention, it was unpredictably found thatadhesive formulations for transparent, residuelessly redetachment-freeadhesive strips are advantageous in respect not only of technicaladhesive properties but also application-relevant ozone resistance whenthey exhibit a specific viscoeleastic behavior, having been formulatedin fact such that the tan δ at application temperature (here 25° C.) at10 rad/s (frequency of the oscillating shearing stress) is at least 0.20and at 100 rad/s is at least 0.40 (according to test J). Preferably, thetan δ at application temperature (here 25° C.) at 10 rad/s is not morethan 0.40 and at 100 rad/s is not more than 1.00.

An elastomer employed comprises, to an extent of at least 90 wt % (basedon the total elastomer amount), a polybutadiene block copolymer or amixture of different polybutadiene block copolymers. This polybutadieneblock copolymer or these polybutadiene block copolymers are copolymerscomprising polymer blocks predominantly formed by vinylaromatics (Ablocks), preferably styrene, and those predominantly formed bypolymerization of 1,3-butadiene (B blocks). The polybutadiene blockcopolymer is not hydrogenated in the polybutadiene block.

According to one preferred embodiment of the invention, at least onepolybutadiene block copolymer is a triblock copolymer or a highermultiblock copolymer having at least two A blocks. As a triblockcopolymer, it may have a linear A-B-A structure. Likewise possible foruse are block copolymers of radial architecture, and also star-shapedand linear multiblock copolymers. All of the aforementioned polymers maybe utilized alone or in a mixture with one another. Further componentspresent may be A-B diblock copolymers. The weight-average molar mass ofthe block copolymers is customarily between 50 000 g/mol and 500 000g/mol, preferably between 75 000 g/mol and 200 000 g/mol.

The block copolymers of the PSAs preferably possess polystyrene endblocks as A blocks. Instead of the preferred polystyrene blocks, polymerblocks based on other aromatic-containing homopolymers and copolymers asvinylaromatics (preferably C₈ to C₁₂ aromatics), having glass transitiontemperatures of greater than 75° C., may also be utilized, such asα-methylstyrene-containing aromatic blocks, for example. Identical ordifferent A blocks may also be included, furthermore. Glass transitiontemperatures are determined according to test L.

In the context of this invention, A blocks are also referred to as “hardblocks”. B blocks, correspondingly, are also called “soft blocks” or“elastomer blocks”. This reflects the inventive selection of the blocksin line with their glass transition temperatures (for A blocks at least40° C., more particularly at least 60° C., and for B blocks up to −50°C., more particularly not more than −80° C.). These figures pertain tothe pure, unblended block copolymers.

In one advantageous embodiment, the polybutadiene block copolymers havea polyvinylaromatic fraction of 20 wt % to 40 wt %, preferably between25 wt % and 35 wt %. Too low a polyvinylaromatic fraction leads toinadequate physical crosslinking, caused by microphase separation withinthe polybutadiene block copolymers. The physical crosslinking isimportant for the holding performance and the tear strength. In the caseof too high a polyvinlylaromatic fraction, on the other hand, theadhesive loses tack.

The polybutadiene block copolymers resulting from the A and B blocks maycomprise identical or different B blocks, in terms of microstructure(relative ratio of the forms of monomer linkage possible forpolybutadiene, 1,4-cis, 1,4-trans, and 1,2-vinyl: preference is given toa 1,4-fraction (cis+trans) of >75%, very preferably of >90%, based onthe polybutadiene blocks, and a 1,4-cis fraction of >40%, based on thepolybutadiene blocks) and/or of chain length. A high fraction of1,4-linkage and especially 1,4-cis-linkage on the part of the monomerunits in the polybutadiene blocks results in advantageoustension/extension characteristics, resulting in sufficientextensibility, which is important for the residueless redetachment understretching.

In a further preferred embodiment, the fraction of the polybutadieneblock copolymers, more particularly polystyrene-polybutadiene blockcopolymers, in total, based on the overall pressure-sensitive adhesive,is at least 40 wt %, preferably at least 45 wt %. A result of aninadequate fraction of polybutadiene block copolymers is that thecohesion of the PSA is relatively low and, for example, the tip-sheartest is no longer passed.

The maximum fraction of the polybutadiene block copolymers, moreparticularly polystyrene-polybutadiene block copolymers, in total, basedon the overall pressure-sensitive adhesive, is not more than 60 wt %,preferably not more than 55 wt %. Too high a fraction of polybutadieneblock copolymers may have the consequence, in turn, that the PSA isbarely still pressure-sensitively adhesive.

Great preference is given to using an elastomer mixture which, based onthe total amount of elastomer used, comprises at least 50 wt %,preferably at least 60 wt %, of A-B-A triblock copolymer and, as acomplement, 50 wt % or, as a preferred complement, 40 wt % of A-Bdiblock copolymer.

Surprisingly, by means of polybutadiene block copolymer-based adhesives(in suitable combination with the other ingredients required accordingto the invention), the requirements can be met not only in terms ofholding and bonding performance, residueless redetachability, andoptical properties, but also in respect of resistance (oxidative aging),despite the fact that the polybutadiene block copolymers are unsaturatedcompounds, if formulation takes place in accordance with the inventionand, in particular, there is a correspondingly advantageous viscoelasticbehavior present.

Employed as tackifying resin kind 1 is a hydrocarbon resin. Theselection of the tackifying resin kind 1 influences the tinting of theadhesive formulation, its resistance, and the compatibility with theremaining formulation ingredients, especially the polybutadiene blockcopolymer-based elastomer.

Tackifying resin kind 1 includes nonhydrogenated and preferably partlyhydrogenated hydrocarbon resins having a softening temperature (Ring &Ball) of at least 90° C. and preferably of not more than 125° C. Verypreferably the softening temperature is at least 95° C. and not morethan 115° C.

Examples of representatives of tackifying resin kind 1 includehydrogenated and nonhydrogenated polymers of dicyclopentadiene,nonhydrogenated, partially hydrogenated or selectively hydrogenatedhydrocarbon resins based on C₅, C₅/C₉ or C₉ monomer streams, polyterpeneresins based on α-pinene and/or β-pinene and/or δ-limonene. Hydrocarbonresins preferably have a Gardener value of <1. The Gardener value isdetermined according to ASTM D1544. It involves dissolving 50 wt % ofresin in 50 wt % of toluene and investigating the color using referencespecimens.

Tackifying resins of tackifying resin kind 1 having a softeningtemperature of not more than 110° C. have a degree of hydrogenation ofbetween 90% and 0% (where 100% means fully hydrogenated and 0%nonhydrogenated), preferably between 90% and 50%.

Tackifying resins of tackifying resin kind 1 having a softeningtemperature of greater than 110° C. have a degree of hydrogenation ofbetween 70% and 0%, preferably between 70% and 50%.

The selection of the correct degree of hydrogenation is important inrelation to the compatibility of the tackifying resins with theelastomers.

Tackifying resin kind 1, where it comprises a partly hydrogenatedtackifying resin, is employed, according to a further preferredembodiment of the invention, in a fraction of at least 25 wt % and notmore than 60 wt %, preferably at least 30 wt % and not more than 50 wt %(based on the adhesive composition).

Tackifying resin kind 1, where it comprises a nonhydrogenated tackifyingresin, is employed, according to a further preferred embodiment of theinvention, in a fraction of at least 15 wt % and not more than 30 wt %,preferably at least 18 wt % and not more than 28 wt % (based on theadhesive composition).

Tackifying resin kind 2 is employed depending on the selection oftackifying resin kind 1.

Employed as tackifying resin kind 2 is a hydrocarbon resin(nonhydrogenated, partly or fully hydrogenated), a terpene-phenolicresin or a rosin (nondisproportionated or disproportionated, partly orfully hydrogenated). Tackifying resin kind 2 substantially influencesthe balance between holding performance (cohesion) and bondingperformance (adhesion).

The degree of hydrogenation of the tackifying resins of tackifying resinkind 2 is at least 0% and not more than 100%, preferably not more than70%. If the resin is unhydrogenated or only slightly hydrogenated, thentypically as little as possible is used, since otherwise there may betinting of the adhesive.

Resins of tackifying resin kind 2 have a softening temperature of atleast 90° C. and preferably not more than 115° C.

Tackifying resins of tackifying resin kind 2 having a softeningtemperature of at least 90° C. and not more than 105° C. are employed upto a proportion of amount of resin kind 1 to amount of resin kind 2 of1:1.

Tackifying resins of tackifying resin kind 2 having a softeningtemperature of >105° C. are employed (based on the total adhesive) in aproportion of not more than 25 wt %, preferably not more than 15 wt %.

If a resin having a softening temperature of not more than 110° C. isused as tackifying resin kind 1, then there is no need for tackifyingresin kind 2, though it can be selected in order to carry outfine-tuning of the technical adhesive properties in accordance withrequirements.

At least one of the resins of resin kind 1 and resin kind 2 is partlyhydrogenated. The proportion of partly hydrogenated resin in the totaladhesive is preferably at least 25 wt %, very preferably at least 30 wt%.

Where only one tackifying resin is employed, it is a partly hydrogenatedtype.

The total tackifying resin content of the adhesive is at least 30 wt %,preferably at least 40 wt %, and not more than 60 wt %, preferably notmore than 50 wt %.

The plasticizing resin serves for the final fine-tuning of thecohesion/adhesion balance. Very preferably it comprises a plasticizingresin or plasticizing-resin mixture having a melt viscosity at 25° C.and 1 Hz of at least 25 Pa*s, preferably of at least 50 Pa*s, and asoftening temperature of <25° C. The melt viscosity is determinedaccording to test K. The plasticizing resin may very preferably be ahydrocarbon-based or a rosin-based plasticizing resin. In relation tothe total adhesive formulation, the plasticizing resin orplasticizing-resin mixture is employed with a fraction of 0 wt % and notmore than 6 wt %, based on the total adhesive composition.

Protectants in particular may be added as further additives to theadhesive. They include primary and secondary aging inhibitors, light andUV stabilizers, and flame retardants, and also fillers, provided theoptical properties still meet the stated requirements.

Typical amounts for use of an additive are up to 1 wt %, based on thetotal adhesive composition. Particularly advantageous are aginginhibitors which leave behind no colored residues on bonding substrates(in this regard, see the prior art in EP 1 341 862 B1). Fillers can beadded at higher levels, typically in a fraction of up to 5 wt %, basedon the total adhesive composition.

The following may typically be utilized as additives:

-   -   plasticizing agents such as, for example, plasticizer oils, or        low molecular mass liquid polymers, such as low molecular mass        polybutenes, for example    -   primary antioxidants such as sterically hindered phenols, for        example    -   secondary antioxidants, such as phosphites or thioethers, for        example    -   process stabilizers such as C-radical scavengers, for example    -   flame retardants    -   light stabilizers such as UV absorbers or sterically hindered        amines, for example    -   dyes    -   processing aids    -   (nano)fillers such as, for example, silicon dioxide, aluminum        oxide, titanium dioxide, or phyllosilicates, and also color        pigments and dyes (for transparent versions nevertheless with        specific coloration), and also optical brighteners    -   endblock reinforcer resins and also    -   optionally further polymers of preferably elastomeric type;        elastomers which can be utilized accordingly include those based        on pure hydrocarbons, as for example polybutadiene, elastomers        with substantial chemical saturation, such as saturated        ethylene-propylene copolymers, α-olefin copolymers,        polyisobutylene, butyl rubber, ethylene-propylene rubber, for        example, and also chemically functionalized hydrocarbons such as        halogen-containing, acrylate-containing, allyl- or vinyl        ether-containing polyolefins, for example.

It should be emphasized that the adhesive of the invention isantiozonant-free.

Explicit mention may be made of particularly advantageous embodiments ofthe invention:

-   A) Pressure-sensitive adhesive comprising, preferably consisting of-   a) an elastomer, the elastomer having a fraction of 40 wt % to 60 wt    %, based on the adhesive composition, and an elastomer used    comprising only polybutadiene block copolymers,-   b) a partly hydrogenated hydrocarbon resin (resin kind 1) having a    softening temperature of at least 90° C., the tackifying resin    having a fraction of 40 wt % to 60 wt %, based on the adhesive    composition.-   B) Pressure-sensitive adhesive comprising, preferably consisting of-   a) an elastomer, the elastomer having a fraction of 40 wt % to 60 wt    %, based on the adhesive composition, and an elastomer used    comprising only polybutadiene block copolymers,-   b) a nonhydrogenated hydrocarbon resin (resin kind 1) having a    softening temperature of at least 90° C., the resin kind 1 having a    fraction of 15 wt % to 30 wt %, based on the adhesive composition,-   c) a further tackifying resin of resin kind 2, having a softening    temperature of at least 90° C., the resin kind 2 having a fraction    of 15 wt % to 30 wt %, based on the adhesive composition.-   C) Pressure-sensitive adhesive comprising, preferably consisting of-   a) an elastomer, the elastomer having a fraction of 40 wt % to 60 wt    %, based on the adhesive composition, and an elastomer used    comprising only polybutadiene block copolymers,-   b) a partly hydrogenated hydrocarbon resin (resin kind 1) having a    softening temperature of at least 90° C., the resin kind 1 having a    fraction of 30 wt % to 59 wt %, based on the adhesive composition,-   c) a further tackifying resin of resin kind 2, having a softening    temperature of at least 90° C., the resin kind 2 having a fraction    of 1 wt % to 30 wt %, based on the adhesive composition.

Formulations of the invention have the following profile of properties:

Physical Mea- measurement surement Property parameter Unit Value (range)method Cohesion Tip-shear days (d) >10 days, Test A holding powerprefera- bly >18 days Adhesion Peel rate mm/24 h <30 mm/24 h, Test Bprefera- bly <20 mm/24 h Detachment Stripping force N/cm <20 N/cm, TestC behavior prefera- bly <15 N/cm UV Susceptibility % tears <10%,prefera- Test D resistance to tears after bly <3%, very UV storagepreferably 0% Color Color value b* >0, <5 Test E (preferably <3) Trans-Haze % <6.0% (prefera- Test F parency bly <4.0, very preferably <2.5%)Trans- Total % >85%, prefera- Test F parency transmission bly >90% OzoneOptical No susceptible Test I resistance evaluation cracking

Also part of the invention is a transparent adhesive strip which isdetachable by extensive stretching and which is constructedcarrierlessly from this pressure-sensitive adhesive. Production ispreferably solvent-free. Solvent-containing processes, however, are alsoconceivable.

Typical product constructions are adhesive tapes (adhesive transfertapes), adhesive sheets and diecuts (adhesive strips). Layer thicknessesare at least 25 μm, preferably at least 100 μm, and up to 2 mm. Verypreferred layer thicknesses are between about 500 μm and about 800 μm.Diverse application possibilities are also conceivable for adhesivetapes between about 150 μm and about 400 μm.

Adhesive sheets can take on any desired extents in both dimensions.Adhesive tapes are, for example, 2 mm, 5 mm, 10 mm, 20 mm, or 50 mmwide. Adhesive tapes may be in the form of wound rolls.

The general expression “adhesive tape” encompasses, in the sense of thisinvention, all sheetlike structures such as two-dimensionally extendedsheets or sheet sections, tapes with extended length and limited width,tape sections, diecuts, labels, and the like.

Diecuts typically have a length of at least 5 mm. Lengths may also be 10mm, 20 mm, 50 mm, 100 mm, or more.

Widths are typically at least 2 mm. Widths may also be 5 mm, 10 mm, 20mm, 50 mm, or more.

The diecuts are customarily longer than they are broad, with thestretching for redetachment in that case lying advantageously along thelongitudinal axis. All angles of the diecuts may be 90° or deviationstherefrom. Also possible are forms in which the diecut is tapered in atleast one direction and in particular runs to a point. Edges may also berounded.

Adhesive products, especially diecuts, may include grip tab regions,which are not tacky on the top and/or bottom face of the diecut.

This region serves as a grip tab, which is pulled in order to producethe extensive stretching especially in the bond plane, and is thereforenonadhesive preferably on both sides, as a result in particular of theapplication of foil or paper sections.

In another advantageous development, the region may be produced byirradiation, powdering, or neutralization of the adhesive.Alternatively, a varnish or a primer may be applied at the correspondingsites.

The surface, moreover, may be modified by chemical treatment such asetching, in order in each case to generate nonadhesive zones.

Adhesive products are provided in particular on a release liner(preferably siliconized paper or foil). The liner may berelease-furnished on one side. In that case advantageously a second plyof a liner is used to mask the second surface (especially in the case ofdiecuts). The liner may also be release-furnished on both sides. In thatcase it is possible to operate with one liner ply (especially in thecase of adhesive tapes).

Although the core of the invention lies clearly in the use of the PSAsof the invention in single-layer pressure-sensitive adhesive stripsredetachable without residue or destruction by extensive stretchingsubstantially in the bond plane, it would not do justice to theinvention if the PSAs of the invention could not also be used inmultilayer PSA strips. In product designs of this kind as well, theozone stability of formulations according to the invention can beutilized advantageously.

The concept of the invention therefore also encompasses constructionshaving an extensible carrier in the middle of the adhesive strips, inwhich case the extensibility of the carrier must be sufficient to ensuredetachment of the adhesive strip by extensive stretching. Serving forexample as carriers may be highly stretchable films. Examples ofextensible carriers which can be used advantageously are transparentversions from WO 2011/124782 A1, DE 10 2012 223 670 A1, WO 2009/114683A1, WO 2010/077541 A1, WO 2010/078396 A1.

In the case of use in multilayer pressure-sensitive adhesive strips,PSAs of the invention may form the middle, the inner, and the outerlayers of the adhesive strips.

Where adhesives of the invention are used as outer layers, internallayers may be constructed alternatively from adhesives based on styreneblock copolymers saturated in the elastomer block, and on the basis ofstyrene block copolymers unsaturated in the elastomer block.

Single-sidedly pressure-sensitive adhesive strips may be obtained, forexample, by rendering the pressure-sensitive adhesive strip inert on oneside.

The fields of use already mentioned may also be actualizedadvantageously with the adhesive strips of the invention.

On account of the properties outlined, the adhesive strip of theinvention may be used with outstanding effect for the bonding of anarticle on a hydrophilic surface.

Possible further applications of corresponding self-adhesive tapes arefound in DE 42 33 872 A1, DE 195 11 288 A1, U.S. Pat. No. 5,507,464 A,U.S. Pat. No. 5,672,402 A and WO 94/21157 A1, specific embodiments, forexample, in DE 44 28 587 A1, DE 44 31 914 A1, WO 97/07172 A1, DE 196 27400 A1, WO 98/03601 A1, and DE 196 49 636 A1, DE 197 20 526 A1, DE 19723 177 A1, DE 297 23 198 A1, DE 197 26 375 A1, DE 197 56 084 A1, DE 19756 816 A1, DE 198 42 864 A1, DE 198 42 865 A1, WO 99/31193 A1, WO99/37729 A1, and WO 99/63018 A1.

The adhesive strip of the invention can be used advantageously in anassembly where the adhesive strip is bonded between two substrates ofwhich at least one is transparent and/or one substrate is designed insuch a way that a load can be affixed thereto.

The transparent substrate(s) in this case may consist of glass or ofplastics such as polycarbonates, poly(meth)acrylates, or polystyrenes.

The substrate suitable for accommodating a load may be a hook element.Preferably such a substrate is at the same time transparent.

Here, the tip-shear load starting from the substrate on account of theload is transferred to the adhesive strip.

Particularly advantageous versions of the invention are elucidated inmore detail using the examples and figures described below, withoutthereby wishing to impose any unnecessary restriction on the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the pressure-sensitive adhesive strip of the inventionwhere the core layer consists of an adhesive and

FIG. 2 shows the pressure-sensitive adhesive strip of the inventionwhere the core layer consists of a carrier,

FIG. 3 shows how an article is bonded on a substrate using an adhesivestrip as per FIG. 1,

FIG. 4 shows the method for detaching the article bonded with thepressure-sensitive adhesive strip,

FIG. 5 shows dynamic-mechanical profiles of adhesives of the invention,and of materials/formulations employed for comparison, and

FIG. 6 shows the diagrammatic representation for evaluating a glasstransition temperature by test L.

FIG. 7 shows micrographs of adhesive sheets after the ozone test. a) Noozone damage b) slight ozone damage c) severe ozone damage

FIG. 1 shows the pressure-sensitive adhesive strip 10 of the inventionwherein the core layer 1 consists of the adhesive of the invention,which is redetachable by extensive stretching particularly in the bondplane.

The core layer 1 has a region which serves as a grip tab, on whichpulling takes place in order to effect the extensive stretchingparticularly in the bond plane of the core layer 1. This region isrendered nonpressure-sensitive adhesive on both sides by the applicationof preferably siliconized foil or paper sections 6.

FIG. 2 shows the pressure-sensitive adhesive strip 10 of the inventionwherein the core layer 1 consists of a carrier which is redetachable byextensive stretching particularly in the bond plane.

Applied on the carrier 1 are two adhesive layers 2, 3 of the invention,which preferably have the same composition.

FIG. 3 shows how an article 11 is bonded to a substrate 12—a hydrophilicsubstrate, for example—using an adhesive strip 10 as per FIG. 1. Thearticle 11 is a hook. 11 and/or 12 may be transparent in configuration.

FIG. 4 shows the method for detaching the article 11 bonded with thepressure-sensitive adhesive strip 10.

Pulling takes place from the grip tab of the adhesive strip 10 in thedirection of the bond plane, leading to stretching. On account of thestretching, the core layer loses bond strength, and parts from thesubstrate 12.

The stretching of the core layer 1 is continued until separation of thecore layer 1 from the substrate 12 is complete.

FIG. 5 represents the measurement plots for examples 1 to 10, obtainedaccording to test method J. From the data, the advantageous tan δ rangescan be read off.

FIG. 6 shows, diagrammatically, the procedure for determining the glasstransition temperature from a thermogram recorded according to test L.

Test Methods Test A—Tip-Shear Holding Power

For determining the tip-shear strength, the sheet of adhesive undertest, with dimensions of 20 mm×50 mm and provided at one end on bothsides with a nonpressure-sensitively adhesive grip tab region (obtainedby laminated application of 25 μm-thick, biaxially oriented polyesterfilm with dimensions of 20 mm×13 mm), is bonded centrally to apolystyrene base plate with dimensions of 40 mm×20 mm×3 mm(length×width×thickness). Plugged onto the base plate is a steel pin 10cm long, which sits vertically on the plate face. The specimens obtainedare bonded with a force of 100 N to a glass plate (pressing time=5 sec)and left for 5 minutes in the unloaded state. Following application ofthe selected tip-shear load by the hanging-on of a weight (20 N with 50mm lever arm), a record is made of the time taken for the bond to fail(i.e., the tip-shear holding power). The test conditions are 23° C. anda relative humidity of 50%. For many applications, the higher thetip-shear holding power, the better.

Test B—Peel Rate:

For the determination of the peel strength, the pressure-sensitiveadhesive strip specimens under investigation, with dimensions of 20mm×50 mm, are lined by lamination over the whole area, without airbubbles, with a PET film 23 μm thick, after which the second side of theadhesive-sheet strip is lined at one end with a film strip approximately10 mm long, to produce at this end a grip tab region which isnonpressure-sensitively adhesive on both sides. Thereafter, theadhesive-sheet strip under test is adhered by its facing side, withgentle applied finger pressure, to the test substrate (coated woodchipwallpaper: wallpaper=Erfurt Kornung 52, color=alpina white, wallpaperbonded to chipboard panel). The specimens are then pressed for 10seconds under an applied pressure of 100 N per 10 cm² ofpressure-sensitive adhesive surface, followed by conditioning at 40° C.for 15 minutes. The test panels are subsequently fixed horizontally,with the grippable region of the adhesive strips pointing downward. Aclip (20 g) is used to fasten a weight of 50 g to the nonadhesive griptab, and so the resulting peeling load (approximately 0.7 N per 20 mm ofadhesive-strip width) acts orthogonally to the bond plane. After 15minutes and after a further 24 hours, a mark is made of the distancetraveled in peel by the adhesive strip from the bond substrate from thebeginning of the test. The distance between the two marks is reported aspeel travel (units: mm per 24 h). For many applications, the lower thepeel travel, the better.

Test C—Stripping Force:

For the determination of the detachment force (stripping force), a sheetof adhesive with dimensions of 50 mm*20 mm (length*width), withnonpressure-sensitively adhesive grip tab region at the top end, isbonded centrally between two steel plates (arranged congruently to oneanother) with dimensions of 50 mm×30 mm. The specimens thus obtained arepressed on with a force of 500 N for 5 seconds, after which they areleft in the unloaded state for 5 minutes. The steel plates each have abore at their bottom end to accommodate an S-shaped steel hook. Thebottom end of the steel hook carries a further steel plate, which allowsthe test arrangement to be fixed for measurement in the lower jaw of atensile testing machine. The bonds are stored at +40° C. for 24 hours.After reconditioning to RT, the adhesive-sheet strip is removed at apulling speed of 1000 mm/min parallel to the bond plane and withoutcontact with the edge regions of the two steel plates. During thisprocedure, the required detachment force in N is recorded. The parameterreported is the maximum of the stripping stress values in N/cm.

Test D—UV Resistance

In order to test the UV resistance, 10 adhesive strips of each sheet ofadhesive under test, in dimensions of 20 mm×50 mm, provided at one endon both sides with a nonpressure-sensitively adhesive grip tab region(obtained by laminating application of 25 μm-thick, biaxially orientedpolyester film of dimensions 20 mm×13 mm), are bonded between two glassplates. The bond is made such that the grip tab protrudes from thebondline by 10 mm. Prior to the application of the second glass plate,each adhesive strip is pressed on with a force of 100 N. The adhesivestrips are then irradiated for seven days with a sunlight lamp (OsramUltra Vitalux 300 W) through the glass plate from a distance of 80 cm.The test temperature is 25° C. After the seven day storage, the adhesivestrips are parted by pulling, with pulling taking place at an angle of15°. The number of torn adhesive strips is recorded. The result isreported in % torn adhesive strips.

Test E—Color Value b*:

The procedure is as per DIN 6174, and the color characteristics areinvestigated in the CIELab three-dimensional space, formed by the threecolor parameters L*, a* and b*. This is done using a BYK Gardenerspectro-guide instrument, equipped with a D/65° lamp. Within the CIELabsystem L* indicates the gray value, a* the color axis from green to red,and b* the color axis from blue to yellow. The positive value range forb* indicates the intensity of the yellow color component. A whiteceramic tile with a b* of 1.68 was used as reference. This tile alsoserves as a sample holder, onto which the adhesive layer under test islaminated. Colorimetry takes place on the pure adhesive layer at athickness of 650 μm in each case, after the adhesive layer has beenfreed from the release liners.

Test F—Haze (Large-Angle Scattering), Transmission:

The transparency or degree of transmittance, occasionally also referredto merely as transmission for short, and expressed generally in %, isthe ratio of the luminous power arriving at the reverse face of a bodythrough which light is irradiated, to the luminous power incident on thefront face. Transmission is curtailed by reflection and possiblyabsorption.

The equation is therefore as follows:transmittance=(1−reflectance−absorptance). Transmission and haze aredetermined in accordance with ASTM D1003 on a haze-gard plus fromByk-Gardner. The procedure for this was that of ASTM D1003.

For the measurement of large-angle scattering and transmission, theadhesive strip is first adhered without bubbles to a glass microscopyslide precleaned with isopropanol (VWR, ECN 631-1552, #201107).Thereafter a PET film 50 μm thick (Melinex® 401, DuPont Teijin Films) islaminated on using a manual roller, with strict attention paid toabsence of bubbles and absence of dust. The resulting laminate is storedat 60° C. for 3 days and then subjected to measurement.

Test G—Molecular Weight Determination:

The weight-average molecular weight M_(w) was determined by gelpermeation chromatography (GPC). The eluent used was THF, measurementtook place at 23° C. The precolumn used was PSS-SDV, 5μ, 10³ Å, ID 8.0mm×50 mm. Separation took place using the columns PSS-SDV, 5μ, 10³ andalso 10⁴ and 10⁶ each with ID 8.0 mm×300 mm. The sample concentrationwas 4 g/I, the flow rate 1.0 ml per minute. Measurement took placeagainst PS standards. (μ=μm; 1 Å=10′ m).

Test H—Tackifier Resin Softening Temperature:

The tackifier resin softening temperature is carried out according tothe relevant methodology, which is known as Ring & Ball and isstandardized according to ASTM E28.

Test I—Ozone Resistance:

A suitable pen is used to mark two parallel lines 6 cm apart on astoneware tile (V&B Fliesen GmbH, Rotensteiner Weg, 66663 Merzig,article No. 1106TW02). Thereafter a distance of 3 cm in length is drawnin on a sheet of adhesive with dimensions of 50 mm×20 mm (length×width)in the longitudinal direction. The adhesive sheet is then stretched toexactly twice its length and in the extended condition is fixed on thestoneware tile in such a way that the markings on adhesive sheet andtile overlap. The adhesive film is lined with release foil and pressedon the tile with a 2 kg roller-applied weight, so that the tension ofthe adhesive sheet is retained. The sample has its liner removed again,and is then stored open for 72 hours at 25° C. and an ozoneconcentration of 50 pphm in an ozone test chamber (conditioning chamberWK3-180/0 from Weiss Unwelttechnik GmbH with ozone testing unit SIM 6000from Anseros Klaus Nonnenmacher GmbH). When the storage time is over,the specimens are evaluated under a direct light microscope(magnification factor 6.5). Border specimens are shown in FIG. 7.

The specimens are considered ozone-resistant if there is no perceptibledamage (cracks, holes, clouding) of the specimen. Appearance of thiskind is shown in FIG. 1 a.

Test J—DMA:

The dynamic glass transition temperature data are based on thedetermination by means of dynamic-mechanical analysis (DMA) at lowfrequencies (frequency sweep; measuring range: 0.01 to 512 rad/s;temperature: 25° C.; deformation 1%; Rheometric ARES class; parallelplate arrangement, sample thickness 1 mm: sample diameter 25 mm:measuring head: 2000 g spring-mounted with standard force (2 k Bendix)).

Test K—Melt Viscosity:

For the determination of the melt viscosity of the plasticizing resins,a shear stress sweep was carried out in a shear stress-controlled DSR200 N rheometer from Rheometrics Scientific, in rotation. A cone/platemeasuring system with a diameter of 25 mm (cone angle 0.1002 rad) wasemployed; the measuring head was air-mounted and suitable for standardforce measurements. The slot was 0.053 mm and the measuring temperature25° C. The frequency was varied from 0.002 Hz to 200 Hz, and the meltviscosity at 1 Hz was recorded.

Test L—DSC:

The glass transition temperature of polymer blocks in block copolymerswas determined by means of dynamic scanning calorimetry (DSC). For thispurpose about 5 mg of the untreated block copolymer samples were weighedinto an aluminum crucible (volume 25 μl) and closed with a perforatedlid. For the measurement, a DSC 204 F1 from Netzsch was used, and wasoperated under nitrogen for inertization. The sample was cooled first to−150° C., then heated at a heating rate of 10 K/min up to +150° C., andcooled again to −150° C. The subsequent second heating curve was runagain at 10 K/min and the change in the heat capacity was recorded.Glass transitions are identified as steps in the thermogram. The glasstransition temperature is evaluated as follows (see FIG. 6). A tangentis applied in each case to the baseline of the thermogram before {circlearound (1)} and after {circle around (2)} of the step. In the region ofthe step, a balancing line {circle around (5)} is placed parallel to theordinate in such a way that it intersects the two tangents, specificallyso as to form two areas {circle around (3)} and {circle around (4)} ofequal content (between each tangent, the balancing line, and themeasuring plot). The point of intersection of the balancing lines thuspositioned with the measuring plot gives the glass transitiontemperature.

EXAMPLES

In the text below, the invention is elucidated in more detail by anumber of examples.

Preparation of Specimens

All of the kneading compounds were produced in a Küpper model III-P1heatable double-sigma kneader from Aachener Maschinenbau. The jacket ofthe kneader was heated by a thermal oil heating bath from Lauda. A bathtemperature of 190° C. was set here. Throughout the kneading operation,there was an inert gas atmosphere of CO₂. The kneader was operated at 50rpm.

First of all the elastomers were weighed out together with the solidaging inhibitors Irganox 3052 and Irgafos 168 (if present in theparticular formula), and charged to the kneader. Thereafter about 10% ofthe amount of solid resin was added, and kneading took place for 15minutes. Subsequently, at intervals of 10 minutes, one third each of theremaining amount of tackifying resin 1, tackifying resin 2 (if presentin the particular formula), plasticizing resin, and the liquid aginginhibitors and/or light stabilizers (Weston 399 and Tinuvin products,respectively) were added and incorporated.

After the end of the kneading operation, the kneading compounds weretaken from the kneader and allowed to cool to room temperature.

The cooled compositions were placed between two plies of siliconizedrelease paper and pressed to hand specimens with a layer thickness of650 μm, using a hot press from Lauffer GmbH & CO KG, model RLKV 25, at130° C.

Example 1 Comparative

wt. % Elastomer Kraton D1165 PT polystyrene-polyisoprene 24.00% blockcopolymer Tackifying Dercolyte A115 nonhydrogenated 47.00% resin 1hydrocarbon resin Tackifying -/- resin 2 Plasticizing Wingtack 10aliphatic hydrocarbon resin 3.50% resin Further Kraton D1102 CSpolystyrene-polybutadiene 24.00% constituents block copolymer Tinuvin571 0.50% Irganfos 168 0.50% Irganox 3052 0.50%

Example 2 Comparative

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 39.00% blockcopolymer Tackifying Dercolyte A115 nonhydrogenated 45.00% resin 1hydrocarbon resin Tackifying -/- resin 2 Plasticizing Wingtack 10aliphatic hydrocarbon resin 4.50% resin Further Kraton D1118 CSpolystyrene-polybutadiene 10.00% constituents block copolymer Tinuvin571 UV stabilizer 0.50% Weston 399 antioxidant 0.50% Irganox 3052antioxidant 0.50%

Example 3 Inventive

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 38.00% blockcopolymer Tackifying Sukorez SU110 fully hydrogenated 23.50% resin 1hydrocarbon resin Tackifying Sukorez SU100 fully hydrogenated 23.50%resin 2 hydrocarbon resin Plasticizing Wingtack 10 aliphatic hydrocarbonresin 3.50% resin Further Kraton D1118 CS polystyrene-polybutadiene10.00% constituents block copolymer Tinuvin 571 UV stabilizer 0.50%Tinuvin 765 antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Example 4 Comparative

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 39.00% blockcopolymer Tackifying Regalite R1100 fully hydrogenated 30.00% resin 1hydrocarbon resin Tackifying Foral AX fully hydrogenated rosin 16.00%resin 2 Plasticizing Wingtack 10 aliphatic hydrocarbon resin 3.50% resinFurther Kraton D1118 CS polystyrene-polybutadiene 10.00% constituentsblock copolymer Tinuvin 571 UV stabilizer 0.50% Tinuvin 765 antioxidant0.50% Irganox 3052 antioxidant 0.50%

Example 5 Inventive

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 38.00% blockcopolymer Tackifying Regalite R7100 partially hydrogenated 32.00% resin1 hydrocarbon resin Tackifying Piccolyte A115 nonhydrogenated 15.00%resin 2 hydrocarbon resin Plasticizing Wingtack 10 aliphatic hydrocarbonresin 3.50% resin Further Kraton D1118 CS polystyrene-polybutadiene10.00% constituents block copolymer Tinuvin 571 UV stabilizer 0.50%Tinuvin 765 antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Example 6 Inventive

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 38.00% blockcopolymer Tackifying Regalite R7100 partially hydrogenated 37.00% resin1 hydrocarbon resin Tackifying Regalite S5090 partially hydrogenated10.00% resin 2 hydrocarbon resin Plasticizing Wingtack 10 aliphatichydrocarbon resin 3.50% resin Further Kraton D1118 CSpolystyrene-polybutadiene 10.00% constituents block copolymer Tinuvin571 UV stabilizer 0.50% Tinuvin 765 antioxidant 0.50% Irganox 3052antioxidant 0.50%

Example 7 Comparative

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 30.00% blockcopolymer Tackifying Regalite R7100 partially hydrogenated 47.00% resin1 hydrocarbon resin Tackifying Arkon M90 partially hydrogenated 13.00%resin 2 hydrocarbon resin Plasticizing Wingtack 10 aliphatic hydrocarbonresin 3.50% resin Further Kraton D1118 CS polystyrene-polybutadiene5.00% constituents block copolymer Tinuvin 571 UV stabilizer 0.50%Tinuvin 765 antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Example 8 Comparative

wt. % Elastomer Kraton D1118 CS polystyrene-polybutadiene 98.50% blockcopolymer Tackifying -/- resin 1 Tackifying -/- resin 2 Plasticizing -/-resin Further Tinuvin 571 UV stabilizer 0.50% constituents Tinuvin 765antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Example 9 Comparative

wt. % Elastomer Kraton D1165 PT polystyrene-polyisoprene 98.50% blockcopolymer Tackifying -/- resin 1 Tackifying -/- resin 2 Plasticizing -/-resin Further Tinuvin 571 UV stabilizer 0.50% constituents Tinuvin 765antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Example 10 Comparative

wt. % Elastomer Kraton D1102 CS polystyrene-polybutadiene 98.50% blockcopolymer Tackifying -/- resin 1 Tackifying -/- resin 2 Plasticizing -/-resin Further Tinuvin 571 UV stabilizer 0.50% constituents Tinuvin 765antioxidant 0.50% Irganox 3052 antioxidant 0.50%

Measurement Values:

Tip-shear holding Peel Stripping UV Color tan δ 25° C., tan δ 25° C.,Ozone Example power rate test resistance Haze Transmission value b* 10rad/s 100 rad/s resistance #1 >18 4 11 90% 5.25 90.0 16.14 0.73 1.55Slight damage #2 >18 8 10  0% 3.20 90.0 13.11 0.49 1.15 No damage#3 >18 >40 8  0% 5.55 90.5 2.33 0.25 0.53 No damage #4 >18 14 8 60% 3.3991.0 4.17 0.17 0.30 Massive damage #5 >18 11 11  0% 5.78 89.7 3.98 0.260.65 No damage #6 >18 15 11 10% 3.82 90.9 3.17 0.24 0.45 No damage #7 26 x x 17.97 90.7 2.09 0.22 0.42 Slight damage #8 x x x x x x x 0.11 0.11Massive damage #9 x x x x x x x 0.08 0.08 Massive damage #10 x x x x x xx 0.06 0.06 Massive damage

1. A pressure-sensitive adhesive at least comprising (a) at least oneelastomer, the elastomer having a fraction of at least 40 wt %, based onthe adhesive composition, and elastomer used comprising at least onekind of a polybutadiene block copolymer, (b) at least one partlyhydrogenated hydrocarbon resin (resin kind 1) having a softeningtemperature of at least 90° C., (c) optionally at least one furtherhydrocarbon resin, a terpene-phenolic resin and/or a rosin having asoftening temperature of at least 90° C. (resin kind 2), (d) optionallya plasticizing resin, (e) optionally further additives.
 2. Apressure-sensitive adhesive at least comprising (a) at least oneelastomer, the elastomer having a fraction of at least 40 wt %, based onthe adhesive composition, and elastomer used comprising at least onekind of a polybutadiene block copolymer, (b) at least onenonhydrogenated hydrocarbon resin (resin kind 1) having a softeningtemperature of at least 90° C., (c) at least one further at least partlyhydrogenated or disproportionated hydrocarbon resin, terpene-phenolicresin and/or rosin having a softening temperature of at least 90° C.(resin kind 2), (d) optionally a plasticizing resin, (e) optionallyfurther additives.
 3. The pressure-sensitive adhesive of claim 1,wherein the tan δ of the pressure-sensitive adhesive at applicationtemperature (here 25° C.) at 10 rad/s is at least 0.20 and at 100 rad/sis at least 0.40, and preferably at application temperature (here 25°C.) at 10 rad/s is not more than 0.40 and at 100 rad/s is not more than1.00.
 4. The pressure-sensitive adhesive of claim 1, wherein thefraction of the polybutadiene block copolymer or of the mixture ofdifferent polybutadiene block copolymers in the elastomer is at least 90wt % (based on the total elastomer amount).
 5. The pressure-sensitiveadhesive of claim 1, wherein at least one polybutadiene block copolymeris a triblock copolymer or a higher multiblock copolymer having at leasttwo A blocks.
 6. The pressure-sensitive adhesive of claim 1, wherein thepolybutadiene block copolymers have a polyvinylaromatic fraction of 20wt % to 40 wt %.
 7. The pressure-sensitive adhesive of claim 1, whereinthe fraction of the polybutadiene block copolymers, in total, based onthe overall pressure-sensitive adhesive, is at least 40 wt %, and themaximum fraction of the polybutadiene block copolymers, in total, basedon the overall pressure-sensitive adhesive, is not more than 60 wt %. 8.The pressure-sensitive adhesive of claim 1, wherein elastomer usedcomprises an elastomer mixture consisting of A-B-A triblock copolymerand A-B diblock copolymer, the fraction of A-B-A triblock copolymer,based on the total amount of elastomer used, being at least 50 wt %. 9.The pressure-sensitive adhesive of claim 1, wherein the total tackifyingresin content in the pressure-sensitive adhesive is at least 30 wt %,and not more than 60 wt %.
 10. The pressure-sensitive adhesive of claim1, wherein the fraction of resin kind 1 is at least 25 wt % and not morethan 60 wt % (based on the adhesive composition).
 11. Thepressure-sensitive adhesive of claim 1, wherein the fraction ofplasticizing resin or plasticizing resin mixture is between 0 wt % and 6wt %, based on the total adhesive composition.
 12. A single- ordouble-sidedly bonding adhesive-sheet strip, which is optionallycarrier-free and hence of only single-ply configuration, comprising thepressure-sensitive adhesive of claim
 1. 13. A method for bonding anarticle to a hydrophilic surface wherein said article is bonded to saidhydrophilic surface with an adhesive-sheet strip of claim
 12. 14. Abonded assembly comprising the adhesive strip of claim 12, the adhesivestrip being bonded between two substrates, of which at least one istransparent and/or one substrate is designed in such a way that a loadcan be affixed thereto.
 15. The pressure-sensitive adhesive of claim 2,wherein the fraction of tackifying resin kind 1 is at least 15 wt % andnot more than 30 wt % (based on the adhesive composition).